Combustion equipment for gas-turbine engines with support means for supporting the flame tube from an air casing



O 11 1955 G. OULIANOFF ET AL 2,720,080

COMBUSTION EQUIPMENT FOR GAS-TURBINE ENGINES WITH SUPPORT MEANS FORSUPPORTING THE FLAME TUBE FROM AN AIR CASING 4 Sheets-Sheet 1 Filed Jan.23, 1953 1955 G. OULIANOFF ETAL 20,080

CQMBUSTION EQUIPMENT FOR GAS-TURBINE ENGINES WITH SUPPORT MEANS FORSUPPORTING THE FLAME TUBE FROM AN AIR CASING Filed Jan. 25, 1953 4Sheets-Sheet 2 Oct. 1., 1955 e. OULIANOFF ET AL COMBUSTION EQUIPMENT FORGAS-TURBINE ENGINES WITH SUPPORT MEANS FOR SUPPORTING THE I FLAME TUBEFROM AN AIR CASING 4 Sheets-Sheet 3 Filed Jan. 23, 1953 A E W HW Wmllllllll 1 Z A g O 1955 v G. OULIANOFF ET AL COMBUSTION EQUIPMENT FORGAS-TURBINE ENGINES WITH SUPPORT MEANS FOR SUPPORTING THE FLAME TUBEFROM AN AIR CASING F iled Jan. 25, 1953 United States Patent fitice2,720,080 Patented Oct. 11, 1955 COMBUSTION EQUIPMENT FOR GAS-TURBINEENGINES WITH SUPPORT MEANS FOR SUP- PORTING THE FLAME TUBE FROM AN AIRCASING George Oulianotf, Allestree, and Jeffrey Evans, Alvaston,

England, assignors to Rolls-Royce Limited, Derby, England, a Britishcompany Application January 23, 1953, Serial No. 332,812

Claims priority, application Great Britain February 1, 1952 Claims. (31.Gil-39.36)

This invention relates to combustion equipment of gasturbine engines ofthe kind (hereinafter referred to as the kind specified) which comprisesan annular air casing afforded by inner and outer coaxial casing walls,and within the annular space between these walls a flame tube alsohaving inner and outer coaxial walls which are also coaxial with thewalls of the air casing and in spaced relation thereto.

This invention has for an object to provide improved means forsupporting the annular flame tube structure in position within theannular space between the walls of the air casing.

According to this invention, combustion equipment of the kind specifiedcomprises a plurality of struts extending between and interconnectingthe inner and outer walls of the air casing at a location so as tooverlap axially the inlet end of the flame tube, which overlap isaccommodated by complementary inter-engaging notchlike featuresextending from the leading end of the flame tube and from the trailingend of the struts respectively, and a plurality of pins each arranged toextend through aligned bores in a strut and an adjacent portion of theflame tube, thereby to locate the flame tube with respect to the struts.

Preferably the struts are of aerofoil section and are those normallyprovided to divide the inlet section of the air casing into a pluralityof axially-extending diffuser passages preferably the flame tube extendsfrom the trailing edge of each strut part-way only towards its leadingedge.

In one preferred embodiment, the entry portion of a flame tube isannular and of wedge section with the apex of the wedge facing the inletof the air casing and with the surfaces of the wedge substantiallyparallel to the inner and outer walls of the expansion chamber sectionof the air casing, which walls diverge in the direction of flow of airtherethrough. In this preferred embodiment the trailing edge of eachstrut is, in effect, cut away towards its leading edge to form twosurfaces respectively parallel to the inner and outer walls of the flametube, and the flame tube is cut away to a shape to conform closely tothe shape of the adjacent portion of the strut. Secured to the flametube to extend between its inner and outer walls adjacent the downstreamend of each cutaway there is a member having a radial bore therethrough,which bore is aligned with bores in the parts of the co-operating strutwhich lie radially inwards and radially outwards of its cutaway portionof the strut. An elongated pin is provided for each set of bores toextend therethrough to locate the flame tube with respect to the strut,and the head of the pin may be received in a socket which is grooved toreceive a circlip for retaining the pin in position.

One embodiment of this invention will now be described by way ofexample, reference being made in the description to the accompanyingdrawings, in which- Figure l is a part-axial section through aconstruction of combustion equipment of the kind specified and embodyingthe invention,

Figure 2 is a section of which the right hand portion is taken on theline 2--2 of Figure 3, and of which the left hand portion is taken onthe line 2A-2A of Figure 4,

Figure 3 is a section on the line 3-3 of Figure 1,

Figure 4 is an enlarged view of the pin and socket connection betweenthe strut and the inlet section of the flame tube, and

Figure 5 illustrates a modification.

The combustion equipment comprises an air casing and a flame tube andeach of these parts is formed in a number of sections joined end to end.

The air casing comprises an expansion chamber section 10 and a mainflame-tube-enclosing section 11 con nected to the downstream end of theexpansion-chamber section 10. Downstream of the section 11 there islocated the nozzle box assembly 12 of the gas-turbine engine.

The expansion-chamber section 10 comprises an outer annular wall 10a andcoaxially within it an inner wall 1% and these two walls are connectedtogether by a plurality of hollow, circumferentially-spaced,radiallyextending, aerofoil-section struts 100. The walls 10a and 10band the struts 10c are conveniently formed in one piece as a casting. Aswill best be seen from Figure 1, the walls 10a and 10b diverge in thedirection of air flow through the expansion-chamber section and, as willbest be seen from Figures 2 and 31', the aerofoil struts divide theannular space between the walls 10a and 10b into a plurality ofaxially-extending air passages.

The main flame-tube-enclosing section 11 comprises an outer wall 11a andan inner wall 11b. The upstream end of the outer wall 11a is secured asby bolts to the outlet end of the outer wall 10a of theexpansion-chamber section 10 and the downstream end is inwardly flanged,as indicated at 13, so that the wall may be bolted to the outer casingmember 12a of the nozzle box structure. The outer wall 11a can bewithdrawn axially to expose the flame tube by unbolting it from theother wall parts 10a, 12a and withdrawing it axially over the nozzle boxstructure 12.

The inner wall 11b is formed from sheet metal and has a strengtheningring 14 secured to its upstream end, which ring has. a slidingengagement with a part carried by the outlet end of the wall 10b of theexpansionchamber section 10. The downstream end of the Wall 11b isconnected with adjacent structure in any convenient manner.

The flame tube is formed from sheet metal and comprises an inlet section15, an outer annular wall 16 and an inner annular wall 17. The inletsection 15 is of hollow wedge form, and the two divergent surfacesthereof may either form continuations of the annular walls 16, 17, or asshown they may be separately formed so that the sections 16, 17 areseparate from section 15. The annular walls 16, 17 are perforated topermit air flowing in the air casing to pass into the flame tube. Theinlet section 15, and walls 16, 17 may be formed as continuous annularparts, or may be formed of segmental sections suitably secured together.Preferably the inlet section 15 is a continuous annular part and thewalls 16, 17 are formed in a number, say four, of segmental sections.

The inlet section 15 of the flame tube extends from within the mainflame-tube-enclosing section 11 of the the expansion-chamber section 10is such that the inlet 1 section- 15.. of. theflametube overlaps axiallythe hollow aerofoil-section struts 100.

The inlet section of the flame tube is formed of upstream: anda'clownstrearn, sheet-metal; annular parts. The

upstreampartmisroughly of V--'section and provides therapexr end of thesection :15; and the'd'ownstrearn part 18 is trough-like in section andprovides=outer andwinner Walliextensions 18a, 18b of the outer andinnerwalls-of the: upstream part.19. Thewall extensions 18a, 18b arejoggled;attlieir-upstream ends to-provide locating seats for theupstream part 19, and the downstream part 18-also' comprises} a radial;wall' 18%: interconnecting the upstream ends-of. the::wall; extensions:18a, 18b.

Eittett within the: trough of the downstream part 18,

there is an annular series of wall parts 20, each' of'which is basicallyin the form of-afrustum of a cone but is formed.- at: its:larger-diameter end with: diametrically-opposed:flats,. 'which. conformwith the curvature of walls 18a, 18b respectively, and is cut away.along planes which are-.normalto; thewalls'18a, 18b atztheir points ofintersection. Eacht-walbpartr 20., asseen looking along the axisofthe.cone, therefore occupiesasector of the annulus lying between walls18a,18b, and. each part 20 is joined, asby Welding, .to the-adjacentparts20;

Each conical wall part 20 is formed at its smallerdiameter end with acylindrical portion 20a terminating in. an. outwardly-directed. flange.20b which surrounds a circular hole-in theradialwalL18c.

The fuel injectors 34 are. located coaxially within thesmallerrdiameterends. of the. parts 20, the atomising'oritherebetween.The shroud members are mounted. from.

the. conical wall parts. 20 by means of. indentations 37 which extendacross the annular passage and are secured.

as by welding.

In an alternative. construction (Figure 5.) the wall parts 20 may beomitted and the shroud members 36.- secured:

directly. to the wall 18c.

The. flame-tubeis supported at; its inlet end by having the. inletsection 15. secured. to the struts. 100 in the fol-.-

lowing manner.

The. trailing edge of each strut-is formed with a notchlike feature (seeFigures 1 and 4) having, a radially outer surface 21 parallel to theadjacent portion of the.-

outer. wall 18a of. section; 15, a radially-inner. surface; 22

parallel. to; the adjacent. portion of the innerywall'. 18bof the.section 15, and a connecting surface 23' which. isv The.-

parallel to but axially spaced from the wall 18c. connectingsurface. 23-is axially about half-way between the apex of the section. 15. andthetrailing edge of the:

strut.

The upstream part'19 of'the. section 15 is. formed. with,

a series of circumferentially-spaced notch-like cut-away recesses 24(Figure 3), one adjacent each strut 10c, and the part 19'is shaped'withthe inner and outer side edges of the'recesses' 24 conforming to theadjacent circumferentially-facing surfacesof-the strut-10c andthe innerand outer bottom edges lying close to the surface 23.

Sheet-metal blanking pieces 25 are secured tothe part- 19 to stiffen itat the cut-awaymecesses 24 and' to seal otf the aperturesformed; by: thecut-away recesses.

the hole 27.

Each blanking-.pieceZS. has secured to.it'.a: short-peg 26 which.projects :into: a. hole. 27. inthe: surface. 23.: of the: adjacentstrutilom. The:v peg26 :has,=a clearance.-from:.the. edges: of:

The'section 15 is disposed relative'to the trailing edges" of the strutsby inter-engaging the notch-like cut-away recesses 24 with thenotch-like features (21, 22, 23) of the struts, and there is providedlocating means by means of which the section 15 is located axially withrespect to the struts 10c and is centred relative'thereto while. being;

capable of relative thermal expansion with respect-.to the struts.

The locating means comprises a series of socket'members 28, one for eachstrut 100, each of which. socket. members 28 is secured to the wall 18con the side thereof-facing the surface 23 of the associated strut 10'cand extending from close to surface 21 of the associated strut 100 toclose to its surface 22. Each socket member 28 has a bore 28a runningthrough it and with the flame tube in position in the combustion.equipment the bore lines up with radial bores 29, 30 in the strut 100,of which bore 29 extends from the outer surface of wall 10a to thesurface 21 and of which the bore 30 is blind and extends inwards fromsurface 22.

The locating means also comprises a series of pins 31,. one for eachstrut 10c, and each pin 31 extends through. a set of aligned bores 29,28a, 30. Each pin- 31 has a: head 31a received in a socket 32 mounted onthe outer. Wall 10a of the air casing and the. socket isinternallygrooved to'receive a retaining circlip 33- for holding,the pinin position.

The walls 18a, 18b have a-clearance from the surfaces 21, 22 of thestrut 10c, the larger clearanceon. assem-- bly, when the flame tube iscold, being between wall. 18a and surface 21. In operation, theflame-tube is: heated to a greater extent thanthe struts 10c, andexpands relative to the struts and this expansion is accommodated by thesocket members 28 slidingradially with respect to the pins 31. In thisWay the concentricityof the flame tube is maintained.

The. flame tube sections 16, 17 may be of any convenient constructionand one suitable construction isdc.-

scribed in the specification of co-pending application Serial No.332,811 filed January 23, 1953, of; the same.

applicants, now Patent No. 2,709,894, issued June 7, 1955.

We claim:

1. A combustion chamber of the kind employedin an aircraft gas turbineengine comprising an air casing having. an. inlet end and an outlet endand including an inner. annular wall and an outer annular wall, aplurality. of; struts extendingbetween. andinterconnecting saidinner.and outer air casing Walls at the inlet end of the air: casing, a flametube including aninner'annular. wall and anouter annular wall, saidflame tube. walls beingspaced fromthe corresponding air casingwall overpart.at'least. of their length and being. substantially coaxialtherewith, and said' flame. tube Walls defining therebetween.

an annular combustion space, an inlet flame-tube sec. tioninterconnecting said inner and outer flame tube walls at their endsadjacent the inlet endof the air casingaud. overlapping said strutsaxially of. said annular space,, means defining recesses in the ends ofsaid strutsnearest the outlet end of the air casing, said; recessesbeing adapted to receive said inlet flame-tube section, a plurality ofradially-extending boresin said struts, means defining a plurality ofbores in said. inlet flame-tubesec tion adapted to be aligned with theboresin said struts when said inlet section is received in saidrecesses, and. a plurality of pins. each adapted to extend through abore inone. of said struts and an aligned bore in. said flame-tubesection.

2. A combustion chamber of the kind employed. in an aircraft gas turbineengine. comprising an air casing having an inlet end and an outlet endand includingan inner annular wall and an outer annular Wall,.said.wallsbeing divergent at the inlet end of the air. casing, a plu-. rality ofvaxially-extendingstruts having side surfaces -ex-' tending betweenleading and trailing edges and said struts interconnecting said innerand outer air casing walls at the inlet end of the air casing, a flametube including an inner annular wall and an outer annular wall, saidflame tube walls being spaced from the corresponding air casing wallever part at least of their length, and being substantially coaxialtherewith and said flame tube walls defining therebetween an annularcombustion space, a wedge-shaped inlet flame tube sectioninterconnecting said inner and outer flame tube walls at their endsadjacent to the inlet end of the air casing, the apex of the wedge beingdirected towards the inlet end of the air casing and the inner and outersurfaces of the wedgeshaped section being substantially parallel to theinner and outer Walls respectively of the air casing, the struts havingat their trailing edges means defining notch-like recesses, each recesshaving a radially-extending surface forwardly of the trailing edge ofthe corresponding strut and having inner and outer surfaces which areparallel to the divergent inner and outer walls of the inlet end of theair casing respectively and extend rearwards from the radial surface tothe trailing edge of the strut, the wedge-shaped inlet section of theflame tube comprising a series of notch-like recesses circumferentiallyspaced to be aligned with the struts and each of the notch-like recesseshaving a radially-extending surface and a pair of axially-extendingsurfaces which extend from said radially-extending surface of thewedge-shaped inlet section to the leading edge thereof, the notch-likerecesses in the struts being adapted to receive the inlet flame tubesection so that the radially-extending surfaces of the wedge-shapedinlet section and of the struts lie parallel to and adjacent to oneanother, and so that the axially-extending surfaces of the wedge-shapedinlet section lie alongside the side surfaces of the struts and theinner and outer surfaces of the recesses in the struts lie alongside theinner and outer surfaces of the wedgeshaped inlet section, a pluralityof radially-extending bores in said struts opening into the recesses inthe struts, means defining a plurality of bores in said wedge-shapedinlet section adapted to be aligned with the bores in said struts whensaid wedge-shaped inlet section is received in said recesses in thestruts, and a plurality of pins each adapted to extend through a bore inone of said struts and an aligned bore in said wedge-shaped inletsection.

3. A combustion chamber as claimed in claim 2, wherein saidradially-extending surfaces or" the notch-like recesses in thewedge-shaped inlet section carry each a short axially-extending peg, andwherein the radiallyextending surfaces in the recesses of the struts areformed each with an axially-extending hole to be engaged by acorresponding one of the pegs.

4. A combustion chamber as claimed in claim 2, wherein the meansdefining a plurality of bores in said wedgeshaped inlet sectioncomprises in each of its notch-like recesses a socket member extendingbetween the inner and outer surfaces of the wedge-shaped inlet sectionand having a bore adapted to be aligned with a correspondingradially-extending bore in one of the struts when the inlet section isreceived in said recesses in the struts, the pins being adapted each toextend through a bore in one of the struts and the bore in the socketmember.

5. A combustion chamber as claimed in claim 4, wherein each pin has ahead, and the outer end of each of the bores in the struts is formed asa recess to receive the head, and comprising means to retain the pin inposition with its head in the recess.

References Cited in the file of this patent UNITED STATES PATENTS2,552,851 Gist, II. May 15, 1951 FOREIGN PATENTS 620,270 Great BritainMar. 22, 1949

